The present invention relates to a method for the separation of limestone from limestone ore. More particularly, it relates to a method for separating limestone from iron-bearing rock, chert, granite, quartz, and other silicates present in limestone ore, especially calcium carbonate from quartz and/or other silicates.
Limestone is a common mineral and appears in many different concentrations in different limestone containing ores. Also present in these limestone ores are impurities such as chert, iron-bearing rock, granite, quartz, and various other silicates. All such impurities are hereinafter referred to as gangue. The limestone ore as mined must be upgraded to obtain the beneficial properties of the limestone and to produce limestone of the desired quality for commercial uses such as in the glass and cattle feed industries. Further, the limestone for use in cement manufacture must also meet specifications, especially with respect to alkaline material.
It is the general practice to separate limestone from the gangue by methods that have distinguished between the physical properties of the limestone and gangue. Such methods include handsorting or optical sorting of the limestone ore. Handsorting is slow and tedious and is economically unattractive. Optical sorting is limited because of difficulty in the resolution of colors and the difficulty of distinguishing among the various shades of colors in limestone and gangue rock. Limestone ore may be upgraded with respect to alkaline material by selective mining; but with selective mining, much limestone is left unmined and thereby unusable. Flotation concentration has also been used to upgrade limestone, but flotation processing costs are relatively high and as such economically unattractive.